# Scattering

Scattering happens when light waves interact with particles or irregularities in a medium, causing the light to change direction.

• When light encounters obstacles, such as molecules in the atmosphere or imperfections in a surface, it can undergo various processes.
• These include reflection, where the light bounces back like a mirror, as well as refraction, diffraction, and absorption, where the light is bent, spread out, or absorbed by the material.
• Scattering plays a  role in various natural phenomena, such as the colour of the sky, the appearance of clouds, and the shimmering of water surfaces.

Scattering does not take place:

• When parallel rays of light reflect off a smooth, flat surface like a mirror, producing a distortion-free reflection.
• When parallel rays of light reflect off a smooth convex surface (although the reflection appears magnified).
• When parallel rays of light reflect off a smooth concave surface (although the reflection typically appears smaller and inverted).
• When parallel rays of light pass through translucent materials containing dissolved substances like dyes.
• Regular scattering happens when light bounces off a smooth, curved surface in a predictable way, creating a clear and undistorted image.
• Think about a spoon in a glass of water. The smooth, curved surface of the spoon predictably bends the light, making the spoon appear slightly bent or magnified. This is an example of regular scattering.
• Regular scattering often occurs when parallel rays of light hit smooth, transparent objects like raindrops or prisms. In these cases, the light bends (refracts) in a predictable way depending on the angle it hits the object and the materials involved.
• This predictable bending can sometimes separate white light into its component colours, creating a rainbow effect known as chromatic dispersion.
• On a microscopic level, all types of scattering follow the laws of reflection and refraction (Snell’s law).
• Let’s look at two cases of regular scattering in more detail:
• When parallel rays of light with a single wavelength strike and enter an object like a raindrop or prism, their path depends on the initial point of impact, the refractive indices of air and water, and the object’s surface properties.
• When parallel rays of incident light with a single wavelength meet the curved surface of a transparent medium at various points, the different angles at which they strike the surface and experience deflection mainly determine how they scatter as they exit the medium.
##### Random scattering
• Random scattering occurs when a material, due to irregularities or imperfections on its surface, reflects or transmits light rays in various unpredictable directions.
• This scattering can produce a variety of effects:
• Reflected light may appear hazy or lack detail, or there may be no clear reflection at all.
• When light passes through sheets of glass with irregular yet smooth surfaces, random scattering distorts the view of the world beyond, making the image blurry and confused.
• A reflection that is free of the effects of random scattering is called a specular reflection. Mirrors generally produce specular reflections.
##### Diffuse light
• Diffuse light is a specific type of random scattering that occurs when light bounces off rough or uneven surfaces.
• In these cases, the light scatters in all directions, creating a soft, even glow.
• The overall structure and composition of a material can also cause diffuse light.
• This happens when light travels through a medium that contains foreign materials, suspended particles, or has an irregular internal structure or variations in density.
• Translucent materials containing dissolved substances, however, typically don’t cause random scattering because the particles are too small.
• On a microscopic scale, all objects adhere to the law of reflection; however, when surface irregularities are larger than the wavelength of light, the light undergoes scattering leading to diffusion.